In China's largest city of Shanghai, covid-19 cases have risen again as millions remain isolated at home.

Over the previous 24 hours, health officials reported 438 confirmed cases and 7,788 asymptomatic cases. The figures were up from the day before.

health workers wearing protective clothing in Shanghai

China's Covid cases surge as Shanghai begins locking down millions.

The daily case numbers are some of the largest since the virus was first detected in the central city of Wuhan in late 2019.

Residents of the eastern Pudong section were supposed to be allowed to leave their homes on Friday, but their neighbours in the western Puxi section were not allowed to leave for four days.

Millions of people are still confined to their homes despite assurances over the availability of food and health services.

Notices delivered to residents said they were required to self-test for Covid-19 daily and take precautions including wearing masks at home and avoiding contact with family members.

A city official apologized last week for the government's handling of the lock down, and a vice premier demanded improvements during a tour of the city on Saturday.

Sun Chunlan, who sits on the Communist Party's Politburo, urged swift action to stem the spread of COVID-19 in the shortest time possible.

Sun stressed the need for China's hardline approach to be followed.

It is a huge challenge to combat the omicron variant while maintaining the normal operation of core functions in a megacity.

She called for the protection of key industries and institutions and the functioning of supply and industrial chains in the commercial hub.

State media reports indicate that China's president is directing the continuing tough approach while trying to avoid further damage to the sputtering economy and ensure overall stability ahead of a key party congress expected in November.